Silver@silica nanopollen modified membranes for wastewater treatment in membrane bioreactors: limited adverse effects on microorganisms and compelling antifouling properties

Abstract

Silver nanoparticle-based membranes have been explored to enhance antibiofouling performance in water and wastewater treatment. However, their overall performance such as the toxicity to microorganisms in addition to antibiofouling behaviours is not adequately addressed. In this study, novel Ag-immobilized silica nanopollens (Ag@S_np) were combined with polyvinylidene fluoride (PVDF) membranes, which can mitigate fouling in membrane bioreactor (MBR) operations. The antibiofouling behaviours were systemically investigated and the effects of membranes on both sludge activity and bacterial community were evaluated. Long-term operation (75 d) revealed that decoration of Ag@S_np on the membrane surface had compelling antibiofouling behaviours without compromising the effluent quality, activated sludge activity and microbial community diversity. The operation cycle of the test MBR (R2, 32 ± 17 d) was much longer than that of a pristine membrane in the control MBR (R1, 16 ± 7 d). Meanwhile, compared to those in R1, the dehydrogenase activity and specific oxygen uptake rate hardly varied in R2, suggesting that release of silver ions from membranes might have a limited toxic impact on the sludge flocs. The long-term nanosilver exposure did not significantly affect the structure and diversity of microorganisms in the MBR system. The findings of this study would underpin the potential application of the silver-based antibiofouling membrane in MBRs for wastewater treatment.